limiting to "no less than" zero

[Byte_Butcher]

Greetings all,

Too many interests and hobbies have kept me away from electronics for a while, but I'm back again and trying to re-learn what little I knew about PICs....

Todays question is how to easily limit a number to "not less than zero".

I have a number... lets call it "volume" and I want to increment or decrement that number by "step", which could be from 1 to 9.
I want to limit "volume" to no more than 350 at the upper end and no "less" than zero at the low end.

So if I press buttonA then volume increments by the step amount, and if I press buttonB then volume decrements by step amount.

Here's a simple example (of what doesn't work):

 
 volume = 100        'set a default level
 step = 3               'This could be ANY NUMBER FROM 1 TO 9

 
 main:

 if buttonA  then volume = (volume + step) min 350     'this works fine to limit the top end to 350

 if buttonB  then volume= (volume - step)  max 0        'but of course THIS fails, because it's hard to go lower than zero

 LCDOUT $fe, $c0, dec volume

 pause 50
 goto main

 end

So I'm sure that there must be an easy way to limit a number from decrementing "below" zero... ?
Help please?


Thanks much!

Steve

[Charles Linquis]

if buttonB  then 
    if step > volume then 
          volume = 0
    else
         volume= (volume - step) 
    endif
 endif

[Heckler]

This Should (untested as of yet) work...

One thing about programming... there is always more than one way to do the exact same thing... some are more elegant than others... Mine usually falls into the "less elegant, but gets the job done" category

The extra "IF" test should eliminate the need to test for below zero or the "max 0" test.

volume = 100        'set a default level
 step = 3            'This could be ANY NUMBER FROM 1 TO 9

 
 main:

 if buttonA  then volume = (volume + step) min 350     'this works fine to limit the top end to 350
 
 if buttonB and (volume < 3) then  
      volume = 0
      goto Skip1
      endif  
 
 if buttonB  then volume= (volume - step)         'but of course THIS fails, because it's hard to go lower than zero

Skip1:
 LCDOUT $fe, $c0, dec volume

 pause 50
 goto main

 end

[Heckler]

Hey Charles... you beat me to it

When I started my reply, you had not posted yet. I am not sure I like the new code posting window... it gave me fits and I had to start over.

I think I like yours better... but it is fun and informative to try different bits of code and compile each and see how the byte count changes. I have been surprised at times in finding that what you think should be more compact code ends up being more bloated.

[Darrel Taylor]

Yup, there are always lots of ways.

if buttonB then
    volume = volume - Vstep        ; subtract the step
    if volume.15 then volume = 0   ; zero if it went negative
endif

[sayzer]

if buttonB then
 if volume - Vstep >= vstep then
  volume = volume - Vstep
 else
  volume = 0   
 endif
endif

[HankMcSpank]

Straying a little off...

I'm never more than a couple of threads away from having it underlined that I'm still woefully underskilled in this programming melarkey - where's the condition here...

if buttonB then

to my n00b eyes, I'd have thought there should be a condition like "if buttonB = 0 then" or "if buttonB = 1 then"

??